Spontaneous? He's stood there for about 5 seconds with a gormless look on his face before reacting. Since he doesn't speak Portuguese I doubt he was in deep thought about Firmino's words. He spoke with Fat Sam and Walsh at half time and then full time and could have spoken to the ref about it again. At any other point during the 7 week investigation he could have admitted he may have been mistaken, but of course the longer it goes on the harder it is to admit his lie.
Stupid post, the kind of comment I’d expect on rawk